Download Review 1 Electron negative Proton positive Neutron

Review 1
1.
List the three basic elements of an atom and state
the charge of each (positive, negative, or neutral).
Element
Charge
Electron
negative
Proton
positive
Neutron
neutral
2.
An electron forced out of orbit by an external force is
called a Free electron .
3.
Conductors allow many free electrons to flow
when an external electric force is applied.
4.
Which of the following materials are good
conductors?
a. copper
b. plastic
c. silver
d. rubber
5.
e.
f.
g.
h.
aluminum
glass
iron
mica
Semiconductor devices can be manufactured to
allow many electrons to flow in one direction
and few electrons to flow in the opposite
direction
177
Review 2
1.
Elements are identified by the number of
electrons in orbit around the nucleus.
2.
A material that has an excess of electrons is said to
have a negative charge.
3.
A material that has a deficiency of electrons is said
to have a positive charge.
4.
Like charges repel and unlike charges
attract .
5.
The force that is applied to a conductor to cause
current flow is voltage .
6.
Electrons move from a or b .
a. positive to negative
b. negative to positive
7.
With an increase of length or a decrease of crosssection of a conductor, resistance will increase .
a. increase
b. decrease
Review 3
V=I*R .
1. The basic Ohm’s Law formula is
2. When solving circuit problems;
current must always be expressed in ampere ,
voltage must always be expressed in volt ,
and resistance must always be expressed in ohm (Ω) .
3. The total current of a simple circuit with a voltage
supply of 12 volts and a resistance of 24 Ω is 0.5 amps.
From Ohm's law
↓
I = V / R = 12 / 24 = 0.5 A
4. What is the total resistance of a series circuit with
following values: R1=10 Ω , R2=15 Ω , and R3=20 Ω ? = 45
Ω
.
Rt = R1+R2+R3 = 10+15+20 = 45 Ω
5. What is total current of a series circuit that has a 120
volt supply and 60 Ω resistance? 2 amps
From Ohm's law
↓
I = V / R = 120 / 60 = 2 A
6. In the following circuit, the voltage dropped across
R1 is 6 volts and R2 is 6 volts.
1.5 Ω
1.5 Ω
R1
R2
12 V
R1 & R2 are connected In series
↓
Rt = R1+R2 = 1.5+1.5= 3 Ω
It = I1=I2=Vt / Rt = 12 / 3 = 4 A
V1= I1*R1 = 4 * 1.5 = 6 V
V2= I2*R2 = 4 * 1.5 = 6V
7. In the following circuit, voltage dropped across R1 is
71.4 volts and across R2 is 28.6 volts.
100 V
R1 & R2 are connected In series
↓
Rt = R1+R2 = 5+2= 7 Ω
It = I1=I2=Vt / Rt = 100 / 7 = 14.3 A
V1= I1*R1 = 14.3 * 5 = 71.4 V
V2= I2*R2 = 14.3 * 2 = 28.6 V
5Ω
2Ω
R1
R2
Review 4
1. The total resistance of a parallel circuit that has four
20 Ω resistors is 5Ω.
Rt = the value of one resister ÷ the number of resisters
Rt = 20/4 = 5 Ω
2. Rt for the following circuit is 5.45
Ω.
R2
R2
R3
10 Ω
20 Ω
30 Ω
1/Rt = 1/R1+ 1/R2 + 1/R3
1/Rt = 1/10 + 1/20 + 1/30
1/Rt = 3/30 + 1.5/30 + 1/30
1/Rt = 5.5/30
Rt= 30/5.5 = 5.45 Ω
3. Rt for the following circuit is
3.33Ω.
R1
R2
5Ω
10 Ω
Rt = ( R1 * R2 ) ÷ ( R1+ R2 )
Rt = ( 5 * 10 ) / ( 5 + 10 ) = 50 / 15 = 3.33 Ω
4. Voltage available at R2 in the following circuit is
12 volts.
12 V
Vt = 12 v
In parallel circuits the voltage is constant
Vt = V1 = V2
V2 = 12v
R1
R2
5Ω
10 Ω
5. In a parallel circuit with two resistors of equal value and
a total current flow of 12 amps, the value of current
through each resistor is 6 amps.
R1= R2
In parallel circuits the voltage is constant
Vt = V1 = V2
It = I1 + I2
---------------V1/R1 = V2/R2
I1 = V1 / R1
I2 = V2 / R2
→ I1 = I2
→ It = I1 + I2 → 12 = I1+ I2
→ I1 = 6
→ I2 = 6
6. In the following circuit, current flow through R1 is _____
2.4 amps, and through R2 is 1.6 amps.
24 Volts
In parallel circuits the voltage is constant
Vt = V1 = V2 = 12v
-------------From Ohm's law
↓
I1 = V1/R1 = 24/10 = 2.4 amps
I2 = V2/R2 = 24/15 = 1.6 amps
R1
R2
10 Ω
15 Ω
Review 5
1.
Calculate equivalent resistance for R1 and R2 and totalresistance for the entire circuit.
R1 20 Ω
R3 10 Ω
+
R2 30 Ω
_
R1 & R2 are connected In parallel
↓
R1&2 = ( R1 * R2 ) ÷ ( R1+ R2 )
R1&2 = ( 20 * 30 ) / ( 20 + 30 ) = 600 / 50 = 12Ω
R3 & R1&2 are connected In series
↓
R1&2&3 = R3 + R1&2 = 10 + 12 = 22 Ω
2.
Calculate equivalent resistance for R1 and R2 and total resistance for the entire circuit.
R1 30 Ω
+
_
R3 20 Ω
R2 10 Ω
R1 & R2 are connected In series
↓
R1&2 = R1 + R2 = 30 + 10 = 40 Ω
R3 & R1&2 are connected In parallel
↓
R1&2&3 = (R1&2 × R3 ) ÷ (R1&2 + R3 )
R1&2&3 = ( 40 × 20 ) ÷ ( 40 + 20 ) = 800 / 60 = 13.33Ω
Review 6
1. The rate at which work is done is called
power .
2. The basic formulas for power in a DC circuit are:
P=IxV
P = I2 x R
P = V2/R
3. In a circuit with a 12 volt supply and 4 Ω resistance, the power consumed is
36 watts.
--------------P = V2/R
P = 122 / 4 = 144/4 = 36w